2 - basic fortran

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Department of Civil EngineeringUniversity of Malaya

Course Code :KAEA 2101

Course Name :Computer Programming

Chapter 2 :Elementary of Fortran

Prepared By :AP. Dr. Lai Sai Hin
http://rds.yahoo.com/_ylt=A0S020s3DCBNJD0AfRCjzbkF/SIG=123o4esud/EXP=1294032311/**http:/www.mr-accounting.com/images/logo/UM.jpg


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Previous Example: Radioactive decay

PROGRAM Radioactive_Decay!-------------------------------------------------------------------------------------------------------------------------------! This program calculates the amount of a radioactive substance that

! remains after a specified time, given an initial amount and its! half-life. Variables used are:! InitialAmount : initial amount of substance (mg)! Half Life : half-life of substance (days)! Time : time at which the amount remaining is calculated (days)! AmountRemaining : amount of substance remaining (mg)!! Input: InitialAmount, Half Life, Time

! Output: AmountRemaining!-------------------------------------------------------------------------------------------------------------------------------IMPLICIT NONE

REAL :: InitialAmount, Half Life, Time, AmountRemaining

! Get values for InitialAmount, Half Life, and Time.PRINT *, "Enter initial amount (mg) of substance, its halflife (days)"PRINT *, "and time (days) at which to find amount remaining:"

READ *, InitialAmount, Half Life, Time

! Compute the amount remaining at the specified time.AmountRemaining = InitialAmount * 0.5 ** (Time / Half Life)

! Display AmountRemaining.PRINT *, "Amount remaining =, AmountRemaining, "mg"

END PROGRAM Radioactive_Decay

Data Type


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Data Types

Fortran Provides 5 basic data types

Integer

Real

Complex

Character

Logical

Numeric typesConstant/variable

Chapter 3


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Data Types

Integers

A whole number

Positive, negative, or Zero

Does not contain comma or decimal point

0137

+2516

-17745

9,999

16.0

- - 5

7-

Valid integer constants

Invalid


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Data Types

Reals

ordinary decimal numbers, or in exponential notation Positive or negative

Must contain a decimal point, without comma

123.234

-0.01536+56473.02

+56473.

12,345.03

5801.23234E2

123.234 E0

12323.4E-2

123234E-3

Valid real constants

Invalid

Valid exponential representation


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Data Types

Character Strings

Also called strings Sequences of symbols from the Fortran character set

Must be enclosed between double quotes or betweenapostrophes.

PDQ123-A

John Q. Dow

John Q. Doe

Dont

John Q. Doe

John Q. DoeInvalid

Valid


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Data Types

Character Strings


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Data Types

Identifiers

MassSpeed_of_Light

speed-ofLight6FeetVelocityVELOCITYvELocITy

Invalid

Same

e.g.:READ, PRINT

Valid


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Data Types

Variables

Symbolic name used to refer to a quantityInitialAmount, Half Life, Time, AmountRemaining

Variable names are identifiers, must follow the rules for

forming valid identifiers

Necessary to declare the type of each variable in a

Fortran program

REAL :: list

REAL :: InitialAmount, HalfLife, Time, AmountRemaining

INTEGER :: list

CHARACTER (LEN = N) :: list or CHARACTER (N) :: list

CHARACTER (LEN = 15) :: FirstName, LastName

CHARACTER :: Initial

CHARACTER (LEN =15) :: FirstName, LastName*20, Initial*1, City

Length = 1Override the specified length


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Data Types

IMPLICIT NONE Statement


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Variable Initialization

Initial values can be assigned to variables (at compile

time)REAL :: list

REAL :: W, X, Y, Z

REAL :: W = 1.0, X = 2.5, Y = 7.73, Z = -2.956


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Constant Attribute

Fortran allows programmer to specify a constant by including

a PARAMETER attribute in the declaration of the identifier For frequently used constant such as:

INTEGER :: Limit

INTEGER, PARAMETER :: Limit = 50

CHARACTER(2) :: Unit

CHARACTER(2), PARAMETER :: Unit = cm

REAL :: Pi, TwoPi, g

REAL, PARAMETER :: Pi = 3.141593, TwoPi = 2.0*Pi, g = 9.81

REAL, PARAMETER :: BirthRate = 0.1758, DeathRate = 0.1257

Why need to declare attribute ???

Increase readability,

Easier to modification.

Change = (0.1758-0.1257) * Population

Population = Population + Change

:

PopulationIncrease = 0.1758 * populationPopulationDevrease = 0.1257 * Population


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Arithmetic Operations & Functions

Operation

In FortranAddition (+), Subtraction (-), Multiplication (*), Division(/), Exponentiation (**)

B2 - 4AC B ** 24 * A * C

- (A + B) OK

N * -2 not OK N * (-2) (OK)

When 2 constants or variables of the same type arecombined using one of the 4 basic arithmetic operation,the result has the same type as the operands

3 + 4 = 7

3.0 + 4.0 = 7.09.0 / 4.0 = 2.25

9 / 4 = 2


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Arithmetic Operations & FunctionsMixed-Mode Expressions

it is possible to combine integer and real quantities When an integer quantity is combined with a real one,

the integer quantity is converted to its real equivalent,

the result is of real type

???

A real exponent

should be never beused in place of an

integer exponent

or


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Arithmetic Operations & FunctionsMixed-Mode Expressions

4. The standard order of evaluation can be modified using parentheses to enclose

subexpressions, the subexpressions are evaluated first in the standard manner.

5. If the parentheses are nested, the computations in the inner most parentheses are

performed first.

(5 * (115) ** 2) * 4 + 9 (5 * 6 ** 2) * 4 + 9 180 * 4 + 9 720 + 9 729


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Functions

Fortran provides library functions for many of thecommon mathematical operations and functions

SQRT(argument)

argument is a real-valued constant, variable, expression

SQRT(7.0)

SQRT(B**2-4.0*A*C) Nonnegative value only

to calculate SQRT of an integer, necessary to convert it to a real value

SQRT(REAL(7))


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Basic Fortran Functions


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The ASSIGNMENT STATEMENT

Used to assign values to variables

Suppose that Xcoordinate and YCoordinate are real variables, Number and Term

are integer variables.

REAL :: Xcoordinate, Ycoordinate

INTEGER :: Number, Term

Consider the following Assignment Statements

XCoordinate = 5.23

YCoordinate = SQRT(25.0) 5.0

Number = 17

Term = Number / 3 + 2 7


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Mixed-Mode ASSIGNMENT

If an integer-valued expression is assigned to a real variable,the integer value is converted to a real constant and thenassigned to the variable

if N has the value 9, Alpha and Beta are real variable,

Alpha = 3 3.0

Beta = (N + 3) / 5 2.0

If an real -valued expression is assigned to an integervariable, the fraction part of the real value is truncated, the

integer part is assigned to the variableif X has the value 5.75, I, Kappa, Mu are integer variables

I = 3.14159 3Kappa = X / 2.0 2Mu = 1.0 / X 0


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Input / OutputFortran provides 2 types of input/output statements

Type 1

- Explicitly specify the format of input & output.

Type 2: list-directed input/output

- predetermined standard formats that match the input/output

list are automatically provided by the compiler- List-Directed InputREAD *, InitialHeight, InitialVelocity, Time

- List-Directed Output

Execution

100.0, 90.0, 4.5

100.0 90.0 4.5

100.0 90.0

4.5


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Example 1: Velocity and Height of a Projectile

!


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Program Composition and FormatGeneral form of a program in Fortran Heading

PROGRAM name

Opening documentation

Specification Part / Type DeclarationIMPLICIT NONE

Declaration statement

Execution partNonexecutable statements

- provide information, do not cause any specific action to be performed during

execution,

e.g.: PROGRAM statement & type statements

Executable statements- specify actions to be performed during execution

e.g.: Assignment statements, input/output ststements

Subprogram part- contain internal subprogram, chapter 6

END PROGRAM statement


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File Input/OutputInteractive Input/Output So far we assumed the data for the sample program was entered from

the keyboard, and the output was displayed on the screenInput/Output Using File To store input data in a disk file, design the program to read data from

this file, and to store a program output in a disk file.E.g.: Projectile Program- input value are read from file named fig2-6.dat

100.0, 90.04.5

- output to be written to a file named fig2-6.outAt time 4.5000000 secondsthe vertical velocity is 45.8700752 m/secand the height is 4.0570767E+02 meters

Opening Files / OPEN statement- before a file can be used for input or output, it must be opened

OPEN (UNIT = unit-number, FILE = file-name, STATUS = status)unit-number is an integer that will be used to reference this file in a READ or WRITE

statement, status =OLD if the file already exists, or NEW otherwise

OPEN(UINT = 12, FILE = fig2-6.dat, STATUS = OLD)

OPEN(UNIT = 13, FILE = fig-2.6.out, STATUS = NEW)


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File Input/Output Opening Files / OPEN statement

- before a file can be used for input or output, it must be opened

OPEN (UNIT = unit-number, FILE = file-name, STATUS = status)unit-number is an integer that will be used to reference this file in a READ or WRITE

statement, status =OLD if the file already exists, or NEW otherwise

OPEN(UINT = 12, FILE = fig2-6.dat, STATUS = OLD)

OPEN(UNIT = 13, FILE = fig2-6.out, STATUS = NEW)

File I/O- once a file has been given a unit number, data can be read from or written

to that file.

READ (unit-number, *) input-list

WRITE (unit-number, *) output-list

READ (12, *) InitialHeight, InitialVelocity, TimeWRITE (13, *) At time, Time, seconds

WRITE (13, *) the vertical velocity is, Velocity, m/sec

WRITE (13, *) and the height is, Height, maters

At time 4.5000000 seconds

the vertical velocity is 45.8700752 m/secand the height is 4.0570767E+02 meters

Execution

Fig2-6.out


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Example 2: Projectile program with file I/O


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Thank You

2 - basic fortran

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